A frequently encountered problem in orthodontic patients is that the arch width or palate is too narrow. This may result in a deformed and/or elongated arch and crowding of the teeth, which in turn can lead to other medical and dental problems. Devices are available which are intended to overcome these problems. Such devices, known as rapid palatal expansion (RPE) devices, comprise a rigid apparatus that includes a screw mechanism which is rotatable to apply an expansive force to the patient's palate. Over time, the expansive forces delivered by RPE devices results in widening of the palate.
Utilizing known devices, palatal expansion is accomplished by periodically (once or twice daily) turning a jack screw incorporated into the expansion device structure. One shortcoming of known RPE devices is that their palatal expansion capability is limited by the length of the screw and/or the associated structure which transfers the expansive force from the screw to the palate. Furthermore, these devices tend to become structurally unstable as they reach their limits of expansion. Currently available palatal expansion devices may provide up to approximately 11 mm of expansion. Oftentimes, however, the range of palatal expansion required in treating a patient is greater than that which is available from a single device. For example, the initial treatment of a patient with a very narrow palate may require a narrow and compact expansion device. As the patient's treatment progresses and the palatal width increases, the initial expansion device becomes inadequate. As a result, the orthodontist must disconnect the device from the patient's teeth, remove it and replace it with a device having a larger palatal expansion range for continued treatment. This drawback requires the clinician and the patient to devote more chair time during the course of the orthodontic treatment, which adds to the overall expense of the process.
Another drawback associated with known palatal expansion devices is the inability to accurately determine how much rotation of the jack screw is required or has been accomplished. An additional and related drawback is that the jack screw may have a tendency to "unwind," resulting in contraction of the device, a decrease in the force applied to the patient's teeth and palate, and unwanted sagittal movement of the teeth and palate.
Therefore, a need exists for an improved rapid palatal expansion device which overcomes the drawbacks associated with existing palatal expansion devices.